1. Field of the Invention
The present invention relates to the field of television receivers and, more particularly, to the use of point of distribution cards in television receivers.
2. Background Information
Starting in 2004, regulations require all television receivers (televisions) that want to carry a “Digital Cable Ready” label indicating that the television receiver is capable of receiving and decoding various digital cable television formats, must incorporate what is known as a Point of Distribution (POD) card. A POD card is similar to a smart card or PCMCIA card, such as are used in satellite television receivers and computers. The POD cards allow for as needed updating of the encryption that is used in the television receiver to protect the video content from unauthorized copying.
Present specifications for POD cards require the capability of handling two (2) separate encoded video paths. The encrypted data passing through the POD card is MPEG-2 format and must be decrypted using the decryption key in the POD card. Due to the high speed of the data, there can be up to 2.5 watts (W) of power dissipated by the POD card.
Moreover, due to the high speed of data, i.e. several megabytes per second, the internal clock edges are roughly 1 nanosecond, generating electromagnetic interference (EMI) harmonics up to 5 GHz. While this is not a significant problem for the portion of the POD card enclosed in the metalwork of the television chassis, an additional problem exists with respect to the unenclosed portion of the POD card as discovered by the present inventors and shown from various radiation tests.
The classical method of fixing a temperature problem is to either reduce the heat at the source or provide a fan to cool the device. In the present case, the 2.5 W dissipation of the POD card is a specification requirement. One thought was to use metal PCMCIA rails to help conduct the heat from the POD card to the metal enclosure of the television receiver. The cost of tooling such metal rails, however, is currently cost prohibitive.
While a fan could be used for cooling the POD card, the main disadvantage of a fan is the noise. Many televisions are used in places where such fan noise would be considered unacceptable. This is especially true for when the television is off.
From an EMI standpoint, the standard means of limiting the EMI from a POD card is to enclose the exposed portion of the card in a metal box. In order for the customer to change the POD card, the customer has to open the door. In critical applications, an interlock can be provided to ensure that the customer closes the door once the POD card is replaced. Although functional, tooling costs and complexity of the door is not an acceptable solution.
It is thus evident from the above discussion that what is needed is a manner of conducting heat from and shielding electromagnetic interference generated by a POD card, particularly, but not necessarily, with respect to or in a television receiver.
This need and others is accomplished through application of the principles of the subject invention and/or as embodied in one or more various forms and/or structures such as are shown and/or described herein.